1. Field of the Invention
The present invention relates to a material for an electrode, an electrode sheet for an all-solid state secondary battery, an all-solid state secondary battery, and methods for manufacturing an electrode sheet for an all-solid state secondary battery and an all-solid state secondary battery.
2. Description of the Related Art
In the related art, electrolytic solutions have been used in lithium ion batteries. Attempts are underway to produce all-solid state secondary batteries in which all constituent materials are solid by replacing the electrolytic solution with a solid electrolyte. Reliability in terms of overall performance of batteries is an advantage of techniques of using inorganic solid electrolytes. For example, to electrolytic solutions being used for lithium ion secondary batteries, flammable materials such as carbonate-based solvents are applied as media. In the above-described lithium ion secondary batteries, a variety of safety measures are employed. However, there is a concern that disadvantages may be caused during overcharging and the like, and there is a demand for additional efforts. All-solid state secondary batteries in which non-flammable electrolytes can be used are considered as a fundamental solution therefor.
An advantage of all-solid state secondary batteries is the suitability for increasing the energy density by stacking electrodes. Specifically, it is possible to produce batteries having a structure in which electrodes and electrolytes are directly arranged in series. In the above-described structure, metal packages that seal battery cells and copper wires or bus-bars that connect battery cells may not be provided, and thus the energy density of batteries can be significantly increased. In addition, favorable compatibility with positive electrode materials capable of increasing potentials and the like can also be considered as advantages.
Due to the respective advantages described above, all-solid state secondary batteries are being developed as next-generation lithium ion batteries (New Energy and Industrial Technology Development Organization (NEDO), Fuel Cell and Hydrogen Technologies Development Department, Electricity Storage Technology Development Section, “NEDO 2013 Roadmap for the Development of Next Generation Automotive Storage Battery Technology” (August, 2013)). For example, WO2013/121642A describes that it is possible to provide an all-solid state secondary battery having an excellent rate characteristic in which a particulate solid electrolyte and a particulate auxiliary conductive agent are bonded to a surface of a particulate electrode active material in an electrode. JP2011-165410A describes a large-capacity all-solid state lithium ion secondary battery including a solid electrolyte layer which includes lithium ion-conductive crystals and a battery element having a collector layer laminated on at least one of a positive electrode layer or a negative electrode layer. In addition, JP2012-243743A describes an all-solid state lithium ion battery having a positive electrode layer having a high output voltage and a discharge capacity that does not easily decrease due to repetitive charging and discharging by containing a positive electrode active material made of a specific composition and a lithium ion-conductive solid electrolyte.